Mastering SQL View Management: A Step-by-Step Guide

Note: All SQL queries used in the Case study is tested on Oracle.

1.Write a view that combines customer data with the respective account balances.
CREATE VIEW CustomerAccountView AS
SELECT c.CustomerID, c.Name AS CustomerName, a.Balance
FROM Customers c
JOIN Accounts a ON c.CustomerID = a.CustomerID;

The query develops a view named CustomerAccountView that combines information on customers with the respective account balances. It is the combination of data in the Customers and Accounts tables. It brings in the CustomerID, customer's name (Name) and balance (Balance) from the Accounts table. The JOIN is from the field of Customer ID in both tables. The view provides an easy access means of aggregative data without having to write across many different tables every time, therefore enhancing efficiency and simplification of the retrievals of data for reporting .

2.Get all records in CustomerAccountView to list the name of the customer and account balance
SELECT * FROM CustomerAccountView;
This query retrieves all rows from the CustomerAccountView that was used to pull together data in both the Customers and Accounts tables. Using SELECT *, it takes back the CustomerID, CustomerName and Balance for every record. This view simplifies access to the data by presenting all consolidated account information in a form that is easily accessible from the view. It is especially useful for producing reports where you want to appear with customer names along with their account balances without resorting to complex joins in the main query.

3.Create a view such that it displays only accounts which have a positive balance, so that any update through this view does not violate the condition of having a positive balance.
CREATE VIEW ActiveAccounts AS
SELECT *
FROM Accounts
WHERE Balance > 0
WITH CHECK OPTION;
This query creates a view called ActiveAccounts that shows all accounts having a positive balance from the Accounts table. The WITH CHECK OPTION clause guarantees that any update made through this view would not leave any account with a non-positive balance. Which means that if the user attempts to update an account balance through this view to less than or equal to zero, the operation would be rejected. This view helps in maintaining integrity on data. It does so by allowing only records that meet predetermined conditions. Positive balances would be included.

4.Create a read-only view to get any basic information about the customer, like customer identifier, name, e-mail, phone, and address.
CREATE VIEW ReadOnlyCustomers AS
SELECT CustomerID, Name, Email, Phone, Address
FROM Customers
WITH READ ONLY;
The ReadOnlyCustomers view is intended to provide access to the basic information regarding the customers in a scenario without being allowed to update, delete, or insert across this view. It contains all the columns of the Customers table like CustomerID, Name, Email, Phone, and Address. The WITH READ ONLY clause ensures that any kind of modification to data through this view would cause an error and hence it is the best option to provide secure, read-only access to customer details. It is useful when one wants the users to view data with no privileges to update it.

5.Create a view for accounts having a balance over 1000 and update the balance of one such account using this view so that the resultant balance is valid too.
CREATE VIEW HighBalanceAccounts AS
SELECT *
FROM Accounts
WHERE Balance > 1000
WITH CHECK OPTION;

UPDATE HighBalanceAccounts
SET Balance = Balance + 500
WHERE AccountID = 2;
The HighBalanceAccounts view will show accounts whose balance is more than 1000. The WITH CHECK OPTION clause means that any update done through this view will maintain the condition of having a balance of more than 1000. In this update statement, the balance of account with AccountID 2 is increased by 500. This maintains the account in the view by ensuring that the balance exceeds the threshold of 1000. This is helpful in maintaining costly accounts and making sure they are at a particular state while updating.

SQL Views Management - Learn to Create, Update, and Optimize

6.If the view CustomerAccountView is no longer necessary then drop the view to clean up the database schema.
DROP VIEW IF EXISTS CustomerAccountView;
This statement deletes the view named CustomerAccountView from the database if it exists. Using DROP VIEW IF EXISTS ensures that it will only try to drop the view if it exists in the database, and not produce an error if the view is not in the database. Dropping unused and outdated views keeps a clean and efficient database schema. The procedure will clean the databases of unwanted objects which reduces unnecessary items in the databases and makes them easier to handle as well as maintaining performance.

7.You have to implement an inline view that would return the overall amount for each account's transactions to obtain the activity for an account.
SELECT a.AccountID, total.TotalAmount
FROM Accounts a
JOIN (
SELECT AccountID, SUM(Amount) AS TotalAmount
FROM Transactions
GROUP BY AccountID
) total ON a.AccountID = total.AccountID;
This question uses an inline view to summarize the total transaction amount for each account. The inline view (total) will sum the Amount of each of the rows found in the Transactions table, given by the SUM function. Then, it will group these sums by AccountID using a GROUP BY clause. The outer query will join this inline view with the Accounts table, based on the AccountID field and print the AccountID and the TotalAmount that corresponds to the ID. This is helpful to figure out the cumulative tally of each account's transactions for reference in establishing a transaction activity.

8.Create a view that can return a row for every customer containing the sum total spent by that customer in such a way that the sum total spent by any customer is easily available.
CREATE VIEW CustomerTransactionTotal AS
SELECT c.CustomerID, c.Name AS CustomerName, SUM(t.Amount) AS TotalSpent
FROM Customers c
JOIN Accounts a ON c.CustomerID = a.CustomerID
JOIN Transactions t ON a.AccountID = t.AccountID
GROUP BY c.CustomerID
WITH CHECK OPTION;
The CustomerTransactionTotal view brings back the total transaction amount for each customer. The query joins the Customers, Accounts, and Transactions tables together. Data is grouped by CustomerID so that each line in the results aggregates the total spent by that customer with the SUM function on the Amount column. This clause WITH CHECK OPTION ensures that any updates carried out through this view do not violate the aggregated nature of the view. This will allow businesses to analyze customer spending easily and helps identify high-spending customers for targeted marketing.

9.Retrieve all records from the view CustomerTransactionTotal to determine the total transaction amounts for every customer.
SELECT * FROM CustomerTransactionTotal;
This SELECT statement retrieves all the data from the CustomerTransactionTotal view which was built to show the total amount spent by each customer. Using SELECT * it grabs the CustomerID, CustomerName and TotalSpent for each customer. This view then opens up access to the summary of expenditure without having to sift through tons of data, so it is much easier to sort out customer transactions. When clients use a view like this, they quickly and easily know which customers provide significant portions of their transaction totals which helps companies focus more of their customer outreach efforts and dig deeper into financial performance.

10.Attempt to update a record in the ReadOnlyCustomers view to demonstrate that changes are not permitted on read-only views.
-- This will fail
UPDATE ReadOnlyCustomers
SET Email = 'newemail@example.com'
WHERE CustomerID = 1;
This statement attempts to modify the Email address of a customer in the ReadOnlyCustomers view. But the update operation will fail with this view since it has been created with WITH READ ONLY clause, which excludes updating, deleting, and inserting into the view. This restriction will make the view behave as a safe source for information about customers. Testing this query may ensure that read-only views do protect data from changes being made, making it appropriate for situations where data integrity and security are at its paramount.

11.Drop multiple views, such as ActiveAccounts and ReadOnlyCustomers to clean up the schema of the database.
DROP VIEW IF EXISTS ActiveAccounts, ReadOnlyCustomers;
This statement drops the views ActiveAccounts and ReadOnlyCustomers if they exist. The use of the DROP VIEW IF EXISTS clause prevents the command from causing an error if any of the views listed do not exist. Remove unused or obsoleted views-clean and efficient schema in the database. Dropping these kinds of views de-clutters unnecessary objects inside the database and improves the query performance. This can be done on a general basis to maintain an organized and optimized database.

12.Write a view that shows the average amount of every transaction per customer, giving an indication of the spending habits.
CREATE VIEW CustomerAverageTransaction AS
SELECT c.CustomerID, c.Name AS CustomerName, AVG(t.Amount) AS AverageTransaction
FROM Customers c
JOIN Accounts a ON c.CustomerID = a.CustomerID
JOIN Transactions t ON a.AccountID = t.AccountID
GROUP BY c.CustomerID
WITH CHECK OPTION;
The CustomerAverageTransaction calculates average transaction amounts for customers. The query joins the Customers, Accounts, and Transactions tables. It calculates using the AVG function the average transaction amount, AverageTransaction, and it returns its results, GROUP BY CustomerID. Updating from this view with the WITH CHECK OPTION clause prevents violations to the rule of aggregating by customer. This view is beneficial for analyzing average spending patterns, finding average sizes of transactions, and learning about purchasing behavior of customers.

13.All records retrieved from the CustomerAverageTransaction view are consulted to help in evaluating average spending behavior of customers.
SELECT * FROM CustomerAverageTransaction;
This statement brings all the information in view CustomerAverageTransaction. It will thus make available the average amount of transactions for each customer. It fetches CustomerID, CustomerName, and AverageTransaction using SELECT *. Hence, this view is deriving individual customer expenditure trends by displaying the average transaction size from the customers. It allows organizations to spot customers with an average transaction above the overall average, thus allowing for promotions targeted at them and tailoring their marketing strategies. This data may come in handy when analyzing customer segments and fine-tuning sales strategies in general with regard to spend behavior.

14.Implement a view that returns only active customers where the names of the active customers are updated in a condition dependent on the active status.
CREATE VIEW ActiveCustomerNames AS
SELECT CustomerID, Name
FROM Customers
WHERE IsActive = TRUE
WITH CHECK OPTION;

UPDATE ActiveCustomerNames
SET Name = 'Updated Name'
WHERE CustomerID = 1;
The view ActiveCustomerNames contains only those customers which are chosen as active, this is the status condition of their IsActive. In the addition of the WITH CHECK OPTION clause ensures that all updates done using this view do not cause a loss of active status. Update statement Updating the Name of customer with CustomerID 1. It may be updated if the customer is active. It therefore allows management of the records of the customer by updating with integrity in excluding only the inactive customers while providing a focused set of data of active customers.

15.Create a view that returns all the transactions within the last 30 days. Always confirm that changes to this view do not violate the date constraint.
CREATE VIEW RecentTransactions AS
SELECT *
FROM Transactions
WHERE tDate >= CURDATE() - INTERVAL 30 DAY
WITH CHECK OPTION;
This query defines the RecentTransactions view showing all the transactions made in the last 30 days. It is a view of the Transactions table that filters it using the condition tDate >= CURDATE() - INTERVAL 30 DAY. CURDATE() returns the current date. The WITH CHECK OPTION clause ensures that any update done through this view will not violate the date condition. This view is useful to analyze the recent activity by the customer and trend over the last month which helps the firms to concentrate on the current transactions and take decisions on the basis of current data.

16.Retrieve the accounts that have never had any transactions. This can help in revealing non-active accounts.
SELECT a.AccountID, a.CustomerID, a.AccountType, a.Balance
FROM Accounts a
WHERE NOT EXISTS (
SELECT 1
FROM Transactions t
WHERE t.AccountID = a.AccountID );
The query returns all the accounts with no transactions at all. It checks whether there is no entry in the Transactions table for each AccountID in the Accounts table using the NOT EXISTS clause. If there are no records that match, the account is inactive, and the details can be printed. This gives some indication of zero-activity accounts, which might call for engagement with a customer or a review of an account. Knowing about sleeping accounts can assist in maintaining an incredibly active customer base as well as a proper strategy to deal with the accounts.

17.Create the view that will aggregate all transaction details by month so the trends for each month can be observed.
CREATE VIEW MonthlyTransactionSummary
AS
SELECT TO_CHAR(tDate, 'YYYY-MM') AS TransactionMonth,
SUM(Amount) AS TotalTransactions FROM Transactions
GROUP BY TO_CHAR(tDate, 'YYYY-MM')
WITH CHECK OPTION;
The query creates the following view: MonthlyTransactionSummary-by each month, summary of the total transaction amounts. Using Oracle the TO_CHAR function is used to pull the month and year for tDate in the format YYYY-MM. The SUM function will sum up the total amount of transaction (TotalTransactions) for each month. The GROUP BY statement ensures that data gets summed up by the formatted month and year. The WITH CHECK OPTION ensures any modifications-the INSERTs or UPDATEs through the view must comply with the conditions in the SELECT statement thus ensuring data consistency.

18.Create a secure view that will limit an instance of sensitive account data so that only an accounts summary should be available to the right users.
CREATE VIEW SecureActiveAccounts AS
SELECT AccountID, CustomerID, AccountType, Balance
FROM Accounts
WHERE Balance > 0
WITH READ ONLY;
The SecureActiveAccounts view specifies a view that returns a restricted view of active accounts with positive balances. The WITH READ ONLY clause guarantees that no users can be allowed to alter the data; thus, security is improved by eliminating unauthorized changes. The WHERE Balance > 0 condition filters the accounts by only including those with a positive balance; thus, inactive or zero-balance accounts are excluded. It abstracts sensitive details, yet the access of authorized users is limited. Thus, it helps in maintaining privacy of data but provides crucial views of active accounts.

19.Pull the records of high-balance accounts from the SecureActiveAccounts view to filter out potential premium customers.
SELECT * FROM SecureActiveAccounts
WHERE Balance > 50000;
This query will return all those records from the view SecureActiveAccounts based on the choice of a balance over 50,000. Sometimes, this may help identify high-balance accounts, which may be your high-value customers. This group may also make it easier for businesses to conceive targeted marketing strategies or custom services that are provided exclusively to those clients. This protected, read-only view prevents sensitive information from being viewed by an anonymous because one cannot update here; however, this does show very interesting information.

20.Drop a view that is no longer required, such as MonthlyTransactionSummary to keep the schema clean.
DROP VIEW IF EXISTS MonthlyTransactionSummary;
This statement will drop the view MonthlyTransactionSummary if it does exist. The DROP VIEW IF EXISTS statement helps avoid getting an error message in case the view is not present. As views can get unused or obsolete, they should be periodically cleaned up of the database schema, to keep the store neat and clean, as well as increase its performance. It would be nice often to check and eliminate extra views that can be considered necessary for the smooth operation of the database .

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Other Topics for Account Management
Joins With Group by Having Equi Join Joins with Subqueries Self Join Outer Join